Opportunistic pathogens and their health risk in four full-scale drinking water treatment and distribution systems

This study investigated the occurrence of various opportunistic pathogens (OPs) through four drinking water treatment and distribution systems in eastern China. Conventional trains involving coagulation/sedimentation, filtration, disinfection efficiently removed total coliforms from 1700 to 2300 CFU/L influent undetectable levels treated tap water. However, culture-independent qPCR analysis detected Legionella spp., Mycobacterium Mycobacteria avium, Pseudomonas aeruginosa amoeba Acanthamoeba spp. all samples, reaching maximum concentrations 5.33, 4.87, 1.63, 3.85, 4.32 log (gene copies/mL), respectively. Thus, OPs were abundant despite met applicable microbiological standards China (GB 5749–2006). Occurrence correlated positively with turbidity chemical oxygen demand (COD), negatively chlorine residual. Turbidity removal by coagulation COD ozonation (O3) followed biological activated carbon (BAC) filtration was train highest efficiency, ClO2 a more effective disinfectant than NaClO. significantly rebounded (up 11-fold for P. 21-fold M. avium water). quantitative microbial risk (QMRA) showed that potential infection risks still below WHO (10−3) even EPA (10−4) benchmarks. Overall, likely underestimation pathogenic culture-dependent quantification indicator organisms makes it prudent use molecular approaches periodically revisit safety systems.